FIG. 1 is a side-sectional view illustrating a general oil supply apparatus of a linear compressor, and FIG. 2 is a disassembled perspective view illustrating a conventional oil supply valve assembly of the linear compressor.
Referring to FIG. 1, in the linear compressor, the oil is stored on an inside bottom surface of a shell 60 which is a hermetic space, a structure formed by coupling a cylinder 2, a piston 4 and a linear motor 70 to a main body frame 3 is elastically supported in the shell, an oil supply passage 12 and an oil recovery passage 14 are formed on the main body frame 3 to communicate with an oil circulation passage 10 formed between the cylinder 2 and the piston 4, and an oil pumping device 20 and an oil supply valve assembly 30 for supplying the oil to a gap between the cylinder 2 and the piston 4 are installed at one side of the main body frame 3 to communicate with the oil supply passage 12.
The main body frame 3 fixes the cylinder 2 and the linear motor. The piston 4 is linearly reciprocated between a top dead center (TDC) and a bottom dead center (BDC) inside the cylinder 2, for repeatedly performing a suction stroke for sucking a refrigerant into a compression space P formed between the piston 4 and the cylinder 2, and a compression stroke for compressing and discharging the refrigerant.
A suction valve 6 for sucking the refrigerant is installed on a communication hole (not shown) formed at one end of the piston 4, and a discharge valve assembly 8 is installed at the opened end of the cylinder 2. In the discharge valve assembly 8, a discharge valve 8a is elastically supported by a discharge valve spring 8c inside a discharge cap 8b fixed to the opened end of the cylinder 2, for opening and closing the opened end of the cylinder 2.
The oil supply passage 12 and the oil recovery passage 14 are formed in the main body frame 3 and the cylinder 2, for supplying or recovering the oil to/from the oil circulation passage 10 formed between the cylinder 2 and the piston 4. In the oil circulation passage 10, a ring-shaped cylinder groove 2h and a ring-shaped piston groove 4h are formed on the inner circumference of the cylinder 2 and the cuter circumference of the piston 4, respectively, to overlap with each other, for circulating the oil.
The oil supply passage 12 and the oil recovery passage 14 are formed to communicate with the cylinder groove 2h, especially, the TDC direction end of the cylinder groove 2h, respectively.
The oil pumping device 20 includes an oil inflow tube 21, and an oil cylinder 22 communicating with the oil inflow tube 21. A mass member 24 is elastically supported by a pair of oil springs 26a and 26b inside the oil cylinder 22. The oil inflow tube 21 is soaked in the oil stored on the bottom of the shell, and communicates with the oil supply passage 12.
One end of the oil cylinder 22 is fixedly inserted into a stepped mounting groove 3h formed on one surface of the main body frame 3 to communicate with the oil supply passage 12. A fixing cap 28 is fixedly inserted onto the other end of the oil cylinder 22. In the oil cylinder 22, the pair of oil springs 26a and 26b elastically support both ends of the mass member 24 between the main body frame 3 and the fixing cap 28.
As the piston 4 is linearly reciprocated inside the cylinder 2, the main body frame 3 is also vibrated, and as the mass member 24 is linearly reciprocated inside the oil cylinder 22, an inner pressure is varied. Therefore, the oil is sucked into the oil inflow tube 21 and circulated along the oil supply passage 12, the oil circulation passage 10 and the oil recovery passage 14.
As illustrated in FIG. 2, in the oil supply valve assembly 30, a gasket G for preventing oil leakage, an oil valve 34 for controlling oil supply, and an oil sheet 36 and an oil cover 38 for forming a storage space for temporarily storing the oil are assembled and bolt-fastened to a mounting part 32 formed on the other surface of the main body frame 3 to overlap with each other.
In detail, a suction storage groove 32a and a discharge storage groove 32b are formed on the mounting part 32 of the main body frame 3. A communication hole 32h communicating with the oil cylinder 22 and an oil discharge hole 32out communicating with the oil supply passage 12 are formed on the suction storage groove 32a and the discharge storage groove 32b, respectively. An oil suction hole 32 in communicating with the oil inflow tube 21 is formed at one side of the mounting part 32.
The oil valve 34 is formed in a metal plate shape. An oil suction valve 34a and an oil discharge valve 34b are formed at the lower center portion and upper center portion of the oil valve 34, respectively, to be movable in the forward and backward directions, by partially cutting the oil valve 34. An oil suction hole 34 in communicating with the oil suction hole 32 in of the mounting part 32 is formed at one side of the oil valve 34.
The oil sheet 36 is formed in a metal plate shape. A suction storage hole 36a opened and closed by a part of the oil suction valve 34a is formed at the lower portion of the oil sheet 36, and a discharge storage hole 36b contacting the other part of the oil suction valve 34a and the oil discharge valve 34b and being blocked by the oil discharge valve 34b is formed at the upper portion of the oil sheet 36.
An oil suction hole 36 in communicating with the oil suction hole 34 in of the oil valve 34 is formed on the oil sheet 36.
When the oil cover 38 is stacked on the oil sheet 36, a suction storage groove 38a is formed on the oil cover 38 to correspond to the suction storage hole 36a and the oil suction hole 36 in of the oil sheet 36, and a discharge storage groove 38b is formed on the oil cover 38 to correspond to the discharge storage hole 36b of the oil sheet 36. The suction storage groove 38a and the discharge storage groove 38b are isolated from each other. In addition, the suction storage groove 38a and the discharge storage groove 38b are protruded in the opposite direction to the oil sheet facing surface.
In the above-described oil supply valve assembly 30, the gasket Q the oil valve 34, the oil sheet 36 and the oil cover 38 are sequentially stacked on the mounting part 32 of the main body frame 3, and fixedly assembled to each other by bolts.
Accordingly, the oil pumping device 20 generates a pressure difference in the oil cylinder 22 by vibration caused by linear reciprocation of the piston 4 inside the cylinder 2. The oil is sucked into the oil inflow tube 21 communicating with the oil cylinder 22, and stored in the suction storage groove 38a of the oil cover 38. If one side pressure of the oil cylinder 22 increases, the oil suction valve 34a blocks the suction storage hole 36a of the oil sheet 36. Therefore, the oil is supplied from the suction storage groove 38a of the oil cover 38 to the discharge storage groove 38b. 
At the same time, since the oil discharge valve 34b is opened due to a pressure difference between the discharge storage groove 38b of the oil cover 38 and the oil supply passage 12, the oil stored in the discharge storage groove 38b of the oil cover 38 is discharged to the oil supply passage 12 through the discharge storage groove 32b of the mounting part 32. The oil can be supplied by repeating the above process.
In the conventional oil supply valve assembly 30 of the linear compressor, the gasket G, the oil valve 34, the oil sheet 36 and the oil cover 38, which are relatively thin, are coupled to the mounting part 32 formed on the main body frame 3 to overlap with each other. Accordingly, the number of the components is large, the assembly process is complicated, and productivity is reduced.